1. Field of Invention
The present invention relates to liquid crystal panel driving methods, liquid crystal devices, and electronic apparatuses. More particularly, the present invention relates to a temperature compensating technique employed when driving a liquid crystal panel.
2. Description of Related Art
Concerning liquid crystal devices used for various matrix liquid crystal displays, for example, a simple matrix liquid crystal device includes, as shown in FIG. 18, a liquid crystal panel 10, driving circuits (a signal electrode driving circuit 20 and a scanning electrode driving circuit 30) for driving the liquid crystal panel 10, a liquid crystal power supply circuit 40 for supplying various DC power to the driving circuits 20 and 30, and a liquid crystal drive control circuit 50 for controlling the driving circuits 20 and 30 and causing the driving circuits 20 and 30 to output predetermined driving signals to the liquid crystal panel 10. A reference clock signal CK (synchronizing signal) at a predetermined frequency is output from an oscillation circuit 60 to the liquid crystal drive control circuit 50. The liquid crystal drive control circuit 50 causes the signal electrode driving circuit 20 and the scanning electrode driving circuit 30 to output driving signals having frequencies corresponding to the reference clock signal CK to the liquid crystal panel 10.
Concerning the liquid crystal panel 10, as schematically shown in FIGS. 2 and 3, a top polarizer 11, a retardation film 12, a top substrate 13 having striped Y electrodes Y1, Y2, Y3, . . . formed on an inner surface thereof, a liquid crystal layer 15, a sealant 16 for sealing the liquid crystal layer 15, a bottom substrate 18 having striped X electrodes X1, X2, X3, . . . formed on an inner surface thereof, a bottom polarizer 14, and a light diffusing plate 19 are disposed in the order mentioned. The X electrodes X1, X2, X3, . . . and the Y electrodes Y1, Y2, Y3, . . . extend in the mutually intersecting directions of the X electrodes and the Y electrodes. As shown in FIG. 4, pixels P11, P12, P13, . . . are formed in a matrix arrangement by portions of these transparent electrodes which intersect each other. These pixels P11, P12, P13, . . . are provided with the liquid crystal panel 10 formed of the Y electrodes Y1, Y2, Y3, . . . on the top substrate 13, the liquid crystal layer 15, and the X electrodes X1, X2, X3, . . . on the bottom substrate 18.
Concerning this liquid crystal panel 10, the orientation states of liquid crystals in the pixels (liquid crystal cells) are controlled by driving signals applied to the X electrodes X1, X2, X3, . . . and the Y electrodes Y1, Y2, Y3, . . . . As a result, the optical characteristics of the pixels (liquid crystal cells) P11, P12, P13, . . . vary. Various images can be displayed by utilizing differences in the optical characteristics of the pixels P11, P12, P13, . . . .
Referring to FIGS. 5(A) and (B), examples of driving signals used for driving the liquid crystal panel 10 are described. FIGS. 5(A) and (B) are a waveform chart of a driving signal (scanning signal) applied to the Y electrodes Y1, Y2, Y3, . . . , and a waveform chart of a driving signal (image signal) applied to the X electrodes X1, X2, X3, . . . , respectively. In FIGS. 5(A) and (B), the waveforms corresponding to two frame periods are shown.
In FIG. 5(A), in the first frame period H, voltage V5 of the scanning signal is at a non-selecting voltage level, and voltage V1 is at a selecting voltage level. In this selection period, when voltage V6 is applied to the X electrodes X1, X2, X3, . . . , an ON voltage is applied to the liquid crystal layer 15. When voltage V4 is applied to the X electrodes X1, X2, X3, . . . , an OFF voltage is applied to the liquid crystal layer 15. In accordance with such variations in the voltage, the liquid crystal layer 15 controls the polarization of incident light, and an image is thus displayed on the liquid crystal panel 10. These potentials V1, V2, V3, . . . are generated by the liquid crystal power supply circuit 40.
According to the liquid crystal device with the above structure, for example, when one frame period H is 16.6 μsec and 32 X electrodes X1, X2, X3, . . . are driven, one selection period is 518.8 μsec per pixel. Under these conditions, when an image signal repetitively becomes on and off, the maximum frequency of the signal applied to the liquid crystal layer 15 is 1.92 kHz.